I guess you can`t do anything with these objects. Only Bradley knows why the cursor turns blue on them....

What's up with the various objects throughout the game such as the ale barrel in Toad Village, and other things that appear as though you can do something with them, but when you click on them, nothing happens? Are they just scenery, or do they have an actual purpose?

I bet there are at least two reasons why some objects don't interact:
1) it makes it somewhat harder to find the ones you do need; it's more like real life if you can't judge you need something just because a cursor turns blue
2) some items were most probably planned to do something, but there wasn't enough time to implement it (or another reason the code didn't make it).